Answer1. Options C and D are correct
Watson and Crick proposed the double-helical model to explain the structure of DNA. They used the information from the following sources
i. X-ray diffraction data produced by Franklin and Wilkins.
ii. Chemical analysis by Erwin Chargaff (Purines = Pyrimidines: A+G = T+C)
2. Option C is correct.
Many scientists believed that the genetic material would possess a complex structure so that it can encode complex body organization. However, Watson and Crick had a conviction that the structure would turn out to have natural beauty in its simplicity. Both the DNA strands are antiparallel and complementary to each other.